A novel dual functional dendritic monomer containing thermo-responsive and light-responsive groups was designed and prepared via a multi-step process of the diazotization, reduction, substitution, etherification and esterification reaction. The chemical structure of monomer was confirmed by infrared spectroscopy (FTIR), nuclear magnetic resonance (1HNMR and 13CNMR) and mass spectrometry (MS) techniques. The thermo- and light-responsive behaviors of the monomer in water was investigated by ultraviolet and visible spectrophotometry (UV-Vis). The results showed that the lower critical solution temperature (LCST) of the monomer aqueous solution (1 mg/mL) was 12.5 °C and decreased by 6.3 °C after UV light irradiation, meanwhile, it has a good reversibility to the UV-Vis absorption of monomer aqueous solution.